Conventionally, there are cases that an outer-rotor type electric brushless motor is used as an electric fan to cool down a radiator of an automobile. This type of electric motor is provided with a stator that is formed by a coil wound on a plurality of teeth, a bottomed cylindrical rotor yoke that covers the stator from a front, a permanent magnet that is arranged at an inner periphery of the rotor yoke, and a rotating shaft that is provided in a center of the stator in a radial direction and that supports the rotor yoke rotatably.
Also, fan blades are provided on an outer periphery of the rotor yoke. When electric current is supplied to the coil, an electrical field is formed around the stator teeth. As a result, electromagnetic attraction and repulsion which cause the rotor yoke to rotate are generated between the stator teeth and the permanent magnet of the rotor yoke and cooling air is generated in an axial direction of the rotating shaft by the fan blades.
In the aforementioned electric motor, since the rotor yoke rotates on an outer side of the stator, a separate cover is required in order to ensure water-tightness of the interior, and this leads to an increase in size of the electric motor. For this reason, electric motors are usually configured as an open type in which the rotor yoke is exposed, and as a result it is inevitable for water to easily enter from the outside.
For example, the motor that is disclosed in Patent Literature 1 is provided with a structure in which a waterproof wall is provided to prevent the infiltration of water from an air intake at a front surface of the rotor yoke that is provided to cool down the interior, and a drain hole is provided to discharge water to the outside when water intrudes.
Also, a motor holder is provided in the stator so as to block an opening of the rotor yoke. By this motor holder, infiltration of water into the interior of the rotor yoke is suppressed.